1. Field of the Invention
The present invention relates to a process for preparing an acetylene derivative, and more specifically to a process for preparing an acetylene compound by reacting a compound having two or more hydrogen atoms on the .alpha.-located carbon of a carbonyl group with a bis-disubstituted amino-difluoromethane compound or fluoroformamidinium.dbd.halogenide.
2. Related Art of the Invention
Acetylene compounds are extremely useful for the synthetic intermediate of agricultural chemicals and medicines and as a monomer which is convertible into a high strength polymer by crosslinking without variation of a molecular chain structure or development of moisture and other gases.
Thus, the demand has steadily increased. Particularly, it has been reported recently in Japanese Laid-Open Patent HEI 9-71651 and tried that polyimide resin and other polymers having excellent heat resistance, chemical resistance, electrical property and mechanical strength can further enhance these properties by terminating the polymer chain or branch of these polymers with the acetylene compounds or by using the acetylene compounds as an oligomer.
Acetylene derivatives can be commonly prepared by various processes disclosed in patents. For example, Soviet Patent 943234 and Japanese Laid Open Patent HEI 6-145078 have described a process for reacting an acetylene compound with other compounds. Similarly, Japanese Patent SHO 50-3299 and U.S. Pat. No. 3,303,229 have disclosed a process that a compound having a double bond is once halogenated and successively dehydrohalogenated to obtained the acetylene derivative. Further, U.S. Pat. No. 4,120,909 has taught a process for heating a compound having two or more hydrogen atoms on the .alpha.-located carbon to a carbonyl group at 600.degree. C. in the presence of a vanadium catalyst.
The conventional preparation process of hydroxyphenyl-acetylene has been reported, for example, in Izv. Akad. Nauk SSSR Se. r. Khim 1964(11), 2073-4. In the process, 4-hydroxyacetophenone is chlorinated with phosphorus pentachloride, reacted in liquid ammonia in the presence of metallic sodium and ammonium chloride, and successively treated with water to obtain 4-hydroxyphenylacetylene in 46% yield.
Further, Chem. Ber. 99(9), 2822-7(1966) described a process for obtaining 3-hydroxyphenylacetylene in 21% yield by way of five step reactions from 3-benzoyloxybenzaldehyde.
In the process described in Bull. Chem. Soc. Japan 29, 470-1(1956), benzofuran is heat-refluxed in the presence of pyridine and metallic sodium and thereafter treated with water to obtain 2-hydroxyphenylacetylene in 54% yield.
In recent year, Polymer. Prepar. 1993, 34(1), 511-12. and Japanese Laid Open Patent HEI 8-217698 have described a process that 3- or 4-halophenol having a protected hydroxyl group, when necessary, is subjected to coupling with trimethylsilylacetylene or other monosilylacetylene in a triethylamine solvent in the presence of a palladium catalyst and thereafter subjected to removing of the silyl group and where necessary, deprotecting of the hydroxyl group to obtain desired hydroxyphenylacetylene in a considerably high yield of 60 to 80%.
Conventional processes above has low yield, require severe synthetic conditions, employ expensive materials and suffer from other problems in industry. Thus, further improvement has been desired.